The present invention relates to apparatus and a method for handling photographic film within the print-exposure section of a photographic printer.
Photographic printers have a component called a "negative supporting stage". Its purpose is to handle the advancing film in such a way as to prevent scratches or other damage and to keep the film correctly positioned while the print is being exposed. The film must also be kept flat during the exposure. Areas that were not flat would project a blurred image onto the paper. Although the film is handled only at the edges while it advances, it must be secured at all four sides of each individual frame or negative on the film strip to keep it flat enough during print exposure. The film accordingly travels between two flat negative-film masks provided with apertures that match the negatives and that constitute a window for passage of the printing light during exposure of the film. The masks are clamped together with the photographic film between them while the print film and print are being exposed, and are then separated once the requisite frame area has been exposed to keep them away from the film as it advances again.
Due to the mechanism for separating the masks, a lot of space must be reserved in a printer for the negative supporting stage. The published German patent application No. OS 4,130,564 accordingly discloses a device with one moving mask and one stationary mask. The edges of the aperture of the stationary mask that extend across the direction the film advances along are provided with openings. Air is forced through these openings while the film is advancing, keeping it off the mask.
The published German patent application No. OS 2,932,878 discloses a device wherein air is forced against the film while the print is being exposed, instead of while the film is being advanced. The air is injected between the film and a transparent plate. The air forces the negative against a transparent lower plate and accordingly eliminates the need for a mechanical clamping mechanism.